Acoustical structure



Oct. 12, 1948. A. D. PARK ETAL ACOUSTICAL STRUCTURE Filed July 20, 1943FIG.

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FIG. 4

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Patented Oct. 12,1948

ACOUSTICAL STRUCTURE Arthur D. Park and Norman A. Johnson, Lancaster,Pa., assignors to Armstrong Cork Company, Lancaster, Pa., a corporationof Pennsylvania Application July 20, 1943, Serial No. 495,426

6 Claims.

This invention relates to acoustical structures and, more particularly,to a decorative monolithic building structure which is incombustible andpossesses a high coefficient of sound absorption;

Variou acoustical structures have been proposed heretofore. For example,one type included studding secured to abase, and burlap or felt sheetsdisposed thereover and secured to the studding. A second type consistedof artificially perforated metal pans holding sound-absorbing material,the pans being mechanically secured by suitable means to a ceiling.These structures are satisfactory from the standpoint of acoustics; theyare not satisfactory'in an esthetic sense for they are not particularlydecorative or ornamental but present a crude, unfinished, incompleteappearance. Such structures have been used to some extent for theirutilitarian functions but they cannot be used in any place Where it isessential that they constitute an attractive decoration.

When the first structure is in use, the burlap, being susceptible toatmospheric conditions, swells or bellies so that it sags away from thestudding thus presenting an unattractive appearance and necessitatingthat the burlap fabric be removed and tightened, or replaced. In

addition, it is not fireproof which materially decreases the number ofplaces in which such structure might be used. The pan type structure,while fireproof, possesses no decorative value and, in fact, detractsfrom the appearance of any room in which it is used. This metal panstructure, moreover, is expensive, difllcult to erect, and extremelydifiicult to keep clean during use. The disadvantages pointed out abovecontribute towardthe lack of success of such structures even though theypossess a satisfactory coefficient of sound absorption.

The chiefobject of our invention is to eliminate the disadvantagesinherent in prior acoustical structures.

I An object of our invention is to provide an incombustible acousticalstructure attractive appearance. Other objects of our invention will bereadily perceived from thefollowing description.

' This invention relates to an acoustical structure which comprises, incombination, a base, a highly porous, inorganic. sound absorbing backinglayer disposed over the base, and a decorative facing disposed over saidlayer, said facing being composed of inorganic material and possessingsubstantially no acoustical value per so while containing sufficientnatural openings to permit the passage of sound waves therethrough tothe sound-absorbing layer.

The attached drawing illustrates a preferred embodiment of ourinvention, in which Figure 1 is a plan View of the acoustical structureof our invention, the facing being partially removed to'disclose thebacking layer;

Figure 2 is a sectional view of the acoustical structure shown in Figure1;

Figure 3 is a plan view, greatly magnified, of a section of facingmaterial;

Figure 4 is a plan view, greatly magnified, of a section of backingmaterial; and

Figure 5 is a sectional view of a modified form of our invention.

Referring to the drawing, there is illustrated an acoustical structureincluding a backing layer 2 of sound-absorbing material and a decorativefacing 3 0f sound-pervious material having substantially no acousticalvalue per se and possessing sufficient naturally formed openings topermit the passage of sound waves therethrough. A layer of any suitableadhesive 4 secures the backing 2 to a base 5 which may be the ceiling ofa home, office or auditorium. The decorative facing 3 is secured to thebacking 2 by means of a layer 6 of adhesive.

The backing layer 2 is composed of a plurality of blocks of rigid orsemi-rigid mats of inorganic material and possesses a high coefiicientofsound absorption. Such blocks or mat are composed of felted inorganicfibers such as felted mats are rough, irregular and uneven in contourconveyor which carries the pack through a series of automaticoperations, notably, the application of a binding agent, for example aphenol-aldehyde resin, compression to desired density while heating toset the binder, cooling, if desired, while still under compression, andcutting to desired size.

In Figure 4 we have attempted to reproduce a small section, greatlymagnified, of a glass wool fiber mat so produced. It will be noted themat is composed of many enlaced and entangled small or fine fibers andthat it is highly porous. These enlaced and entangled fibers are aidedin their retention in mat form by the phenol-aldehyde binder discussedabove. Such glass fiber are incombustible, a property of greatimportance in this particular application. The fiber mat so producedprovides a maximum of dead air spaces which renders it of particularvalue in the absorption of sound. In addition, such material withstandsheat, rot, dampness and decay thus assuring a. long life in service.

The facing 3 comprises an inorganic material likewise capable ofresisting heat, rot, dampness and decay, and is composed of thin sheetsof felted glass fibers such as the glass fiber material commonly used asa retainer mat in electrical storage batteries. We are not certain as tothe manner in which this particular material is made but we believe itmay be generally similarly to the glass wool mats described above. Thebinder used is believed to be starch; the fibers are generally ofgreater length than the glass wool fibers used in the manufacture of themats and are slightly coarser than such fibers. Such fibers are commonlycalled bonded mat fiber and are purchased in finished sheets having ahighly decorative appearance and so thin as to possess substantially noacoustical value per se.

In Figure 3 we have attempted to reproduce a small section, greatlymagnified, of a bonded wool mat sheet as a ready means of comparisonwith the backing layer. Thus, it will be observed that the fibersforming the facing are considerably greater in length than the fibersforming the backing and are slightly greater in diameter. The sheet soformed is highly porous and presents many natural openings therethroughto permit the passage of sound waves to the sound absorbing backing. Inaddition, the sheet is so thin as to possess substantially no acousticalvalue per se while being sound pervious. The terms naturally formedopenings" or natural openings are used herein to denote openingsnaturally occurring during the formation of the sheet facing incontradistinction to openings artificially formed in the sheet facingafter manufacture thereof.

A sheet composed of bonded wool mat glass fibers is characterized by itstendency to return to its initial position or unfold when bent; thischaracteristic is of particular importance when the sheet is employed asa facing in the manufacture of acoustical structures. As pointed outabove, the facing is generally adhesively secured to the backing.Frequently, at the corners or edges of the room in which the structureis erected, it is necessary that the facing extend for a slight distancewithout support; since the backing is formed of a plurality of mats ofirregular and rough contour so that the joints between adjacent mats areopen and uneven, in many cases, it is necessary that the facing extendthereover without support. Since this particular facing material iscapable of maintaining its planar posimat fiber is applied thereover.

tion without support, it will be appreciated that a more finished andornamental structure may be obtained.

The adhesive used to secure the sound-absorbing backing layer 2 to thebase 5 may comprise a mixture of drying oil, resin and filler carried ina suitable solvent. In securing the facing 3 to the backing 2, we havefound a satisfactory bond may be obtained by dissolving a polymerizedisobutylene of high molecular weight in a suitable solvent such asmethyl chloride, toluol, benzol, etc. It will be understood ourinvention is not limited to the employment of the adhesives describedabove for any suitable adhesives may be used to secure the backing layerto the base and the facing to the backing layer.

In the erection of the acoustical structure of our invention the mats ofglass wool fiber possessing sound-absorbing characteristics areadhesively secured to the base 5. As pointed out above, these mats arerough, irregular, and uneven; consequently the joints therebetween areirregular and apparent to the casual observer. In addition, the exteriorsurface of the mats, when such mats are disposed in the structure, issomewhat irregular. Thus a structure so formed would be unsatisfactoryin itself for, while its coeflicient of sound-absorption would besatisfactory, its appearance would be so unsatisfactory in an estheti-csense as to prevent its use. Accordingly, it is essential that asuitable facin as described above be disposed thereover. A thin layer ofadhesive is spread over the backing layer 2 and while it is still tackythe sheet 3 of bonded This sheet may be applied conveniently in the samemanner, for example, as wallpaper is applied to a plastered surface. Thesheet as previously described is characterized by its inherent tendencyto return to original position when bent; consequently, it serves ineffect to bridge over the irregularities of the backing layer and topresent a substantially planar surface. It is essential in our inventionthat the sheet of bonded mat fiber cover more than one of the matscomposing the backing, since this eliminates :a plurality of joints inthe facing. Similar sheets are disposed over the backing layer and seamsare formed between the sheets by overlapping adjacent sheets slightly,and cutting both sheets through at the same time. This sheet materialcuts with a perfectly clean or sharp edge since cutting the glass fibersamounts to, in effect, breaking each glass fiber at the desired point.Such practice ensures a perfect fit so that the seams formed betweensheets are substantially invisible to the casual observer, whereby thestructure possesses a decorative appearance and forms a highlysatisfactory acoustical ceiling.

The sheet material is somewhat transparent or translucent so that thebacking may appear vaguely therethrough. To eliminate this disadvantage,preferably, the facing 3 is painted with any suitable fiat type interiorpaint. The paint coating may be applied before or after the sheetmaterial is placed in position. It is essential of course that the paintcoating be so applied to the fibers as to adhere to the fibers withoutbridging over the openings therebetween and we have found that anatomized sprayed coating is desirable.

The structure so formed may be characterized as monolithic. It isincombustible and hence may be used in many places where materials ofequivalent coefiicient of sound absorption may not be used. In addition,it provides a ready and easily erected ornamentation for an auditorium,office, or room, as well as providing the usual advantages of asound-absorbing structure.

In Figure 5, we have disclosed a modified form of our invention in whicha mechanical erection ,system is used to secure the sound-absorbingbacking layer to the base. In this structure T bars 1 may be providedwhich are secured by means of wire 8 to the base 5. The sound-absorbingmats 2 of glass wool fiber are provided with openings or recesses intheir edges adapted to receive an arm of bar 1. To erect the structure,the mats are supported by the'bars I, the openings in each mat receivingarms of bars I so that each mat is supported between adjacent bars 1 andrests on the arms thereof. The facing 3 composed of thin sheets ofbonded mat fiber is formed over the backing layer 2 in the mannerdescribed above.

It will be observed our invention possesses numerous advantages. Thematerials composing the structure are incombustible so that thestructure may be erected even in restricted zones. It is attractive inappearance and considerably improves the decorative value of the ceilingon which it is erected. Many attempts have been made with little or nosuccess by manufacturers of acoustical structures to eliminate theundesirable appearance of the joints; our invention provides a structurein which the joints are practically invisible to the casual observer.The structure is quickly and easily formed and unskilled labor may beused in its manufacture. Our invention fulfills a pressing demand byarchitects and decorators for a, simple, plain, easily erected,incombustible, highly sound-absorbing structure Which may be used inrestricted zones.

While we have described and illustrated a preferred embodiment of ourinvention, it will be understood our invention is not limited thereto,since it may be otherwise embodied within the scope of the followingclaims.

We claim:

1. In a sound absorbing structure for walls and other surfaces, a base,a plurality of mats of highly porous, sound absorbing, inorganic fibrousmaterial disposed over the base and presenting a rough and irregularouter surface, and a decorative facing in sheet form disposed over aplurality of said mats and adhesively joined to said mats and presentinga substantially planar exposed surface bridging over the irregularsurface contour and joints between said mats, said facing comprising athin, open, preformed, self- 6 sustaining web of felted glass fiberscharacterized by an inherent tendency to return to its original positionwhen bent and released, which characteristic results in the facing weblying fiat and planar regardless of the irregularities in the soundabsorbing mats to which the web is attached.

2. The combination of claim 1 in which the mats are formed of feltedglass fibers.

3. The combination of claim 1 in which the mats are formed of feltedglass fibers and the facing web is formed of glass fibers of a lengthgreater than the length of the fibers in the mats.

4. The combination of claim 1 in which the mats are secured to the baseby an adhesive.

5. The combination of claim 1 in which the mats are formed of feltedglass fibers and in which the mats are secured to the base by means ofan adhesive.

6. The combination of claim 1 in which T bars are suspended from thebase and in which the mats are supported by said T bars.

ARTHUR D. PARK.

NORMAN A. JOHNSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 612,733 Kelly Oct. 18, 1898880,784 Ferres Mar. 3, 1908 1,442,328 De Long Jan. 16, 1923 1,832,571Nash Nov. 17, 1931 1,869,367 Dean Aug. 2, 1932 1,880,153 RosenzweigSept. 27, 1932 1,910,810 Nash May 23, 1933 2,030,157 Schlenker Feb. 11,1936 2,077,713 Ross et a1 Aug. 2, 1932 2,160,001 Saborsky May 30, 19392,160,638 Bedell et a1 May 30, 1939 2,175,226 Slayter Oct. 10, 19392,234,560 Keyes Mar. 11, 1941 2,355,608 Stieger Aug. 15, 1944 FOREIGNPATENTS Number Country Date 4,914 Great Britain Feb. 27, 1911 128,132Austria "May 10, 1932 442,251 Great Britain Feb. 5, 1936 482,809 GreatBritain Apr. 5, 1938 OTHER REFERENCES The Architectural Forum, page 116,Nov. 1942.

